State identification of electrically conductive oblong tensioning elements using resonance frequencies and a computer program

• US 20040073408A1
• Filed: 10/29/2003
• Published: 04/15/2004
• Est. Priority Date: 01/20/2001
• Status: Abandoned Application

• Current Assignee: Technische Universitat Braunschweig Carolo-Wilhelmina
• Original Assignee: Technische Universitat Braunschweig Carolo-Wilhelmina
• Inventors: Schneider, Guido, Budelmann, Harald, Hariri, Karim, Jacob, Arne, Jannsen, Bert, Wichmann, Hans-Joachim
• Application Number:
  US10/466,247
• Publication Number:
  US 20040073408A1
• Time in Patent Office: Days
• US Class Current: 702/196
• CPC Class Codes: E04C 5/08 Members specially adapted to be used in prestressed constructions production of reinforced objects in general B28B23/00; prestressed structures produced in situ E04G21/12
• CPC Class Codes: G01L 1/005 by electrical means and not provided for in G01L1/06 - G01L1/22
• CPC Class Codes: G01M 5/0025 of elongated objects, e.g. pipes, masts, towers or railways G01M5/0058 takes precedence
• CPC Class Codes: G01M 5/0033 by determining damage, crack or wear
• CPC Class Codes: G01M 5/0091 by using electromagnetic excitation or detection
• CPC Class Codes: G01N 33/383 Concrete, cement

Abstract

The invention relates to a method for identifying the state (point of rupture 2) of electrically conductive oblong tensioning elements (1) involving the following steps: launching an electromagnetic measurment signal into a tensioning element (1a); changing the frequency; measuring the reflection spectrum, and; indentifying the state of the tensioning element (1a) according to the resonance frequencies. Said signal is lauched on the fore-part or on the periphery. In the event of coupled tensioning element (1), a scattering matrix system of equations is iteratively devised. The invention is used in the construction industry for prestressed concrete structures and rear anchored systems.

Claims

1. A method for identifying the state of electrically conductive elongate tensioning elements (1) characterized by

launching an electromagnetic measurement signal into a tensioning element (1a);

changing the frequency of the measurement signal;

measuring the reflection spectrum of the measurement signal;

identifying the state of the tensioning element (1a) according to the resonant frequencies from the reflection spectrum.

2. The method as claimed in claim 1 for identifying the state of a little coupled electrically conductive elongate tensioning element (1), characterized by calculating the rupture length (l_b) from the launching point (3) of the measurement signal to a damage site from the difference between two neighboring resonant frequencies Δ

f by the formula

3. The method as claimed in claim 2, characterized by

carrying out a comparative measurement on at least one corresponding comparison tensioning element (1b, 1c) of the same length;

calculating the rupture length (l_b) of the launching point (3) of the measurement signal to a damage site from the difference between two neighboring resonant frequencies of the tensioning element (1a) Δ

f_l, the difference between two neighboring resonant frequencies of the comparison tensioning element (1b, 1c) Δ

f₂ and the overall length l_g of the comparison tensioning element (1b, 1c) by the formula

$l_{\text{\hspace{1em}<br><br>}<br><br>b}=\frac{l_g<br><br>\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>f_1}{\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>f_2}.$

4. The method as claimed in claim 1 for identifying the state of coupled electrically conductive elongate tensioning elements (1), characterized by

determining the number n, the overall length l_g and the diameter d of the tensioning elements (1) coupled to one another;

determining the dielectric constant ε

_r of the medium which is located between the tensioning elements (1);

devising a scattering matrix system of equations for the model of the coupled tensioning elements (1);

calculating the reflection spectrum for the scattering matrix system of equations;

comparing the calculated reflection spectrum with the measured reflection spectrum;

iteratively adapting the parameters of the scattering matrix system of equations until the calculated reflection spectrum approximately coincides with the measured reflection spectrum;

identifying the state of the tensioning element (1) from the parameters of the scattering matrix system of equations.

5. The method as claimed in claim 4, characterized in that the scattering matrix system of equations comprises five scattering matrices,

a first scattering matrix being intended for the launching portion of the coupled tensioning elements (1),

a second scattering matrix being intended for the distance of the coupled tensioning elements (1) between the launching portion and a point of rupture or fault (2),

a third scattering matrix being intended for the portion of a point of rupture or fault (2),

a fourth scattering matrix being intended for the portion of the coupled tensioning elements (1) between the point of rupture or fault (2) and the termination of the tensioning elements (1), and

a fifth scattering matrix being intended for the terminating portion of the linked tensioning elements (1).

6. The method as claimed in one of the preceding claims, the ends of the tensioning elements (1) not being connected to one another in an electrically conducting manner, characterized by launching the electromagnetic measurement signal at the end face of a tensioning element (1).

7. The method as claimed in one of claims 1 to 5, the ends of the tensioning elements being connected to one another in an electrically conducting manner, characterized by launching the electromagnetic measurement signal on the circumference of a tensioning element (1) at a distance from the end face of the tensioning element (1).

8. The method as claimed in one of the preceding claims, characterized by connecting the remaining tensioning elements (1), on which the electromagnetic measurement signal is not launched, to ground potential.

9. A computer program with program coding means for carrying out the steps according to one of the preceding claims when the computer program is executed on a computer.

10. The computer program with program coding means as claimed in claim 9, which are stored on a computer-readable carrier.